1. Field of the Invention
The present invention relates to automobile air conditioning systems, and more particularly to an electronic control method and apparatus for an automobile air conditioning system which includes an electrically operated switch door for selectively allowing the flow of outside air or the flow of recirculated inside air into a passenger compartment through an air duct of the air conditioning system, and which is associated with an electrically operated air purifier for purifying the polluted air in the compartment.
2. Description of the Prior Art
During operation of an automobile air conditioner installed within a passenger compartment, the windows of the compartment are usually closed or only partially opened to decrease the ventilation rate of the air in the compartment so as to enhance the efficiency of the temperature control and the himidity control. As a result, polluted air is apt to remain in the passenger compartment due to smoking in the compartment or induction of polluted outside air. To rapidly eliminate the polluted air from the passenger compartment, the occupant often has to open the compartment windows, switch over the air induction channel, or activate an electrically operated air purifier. To avoid the trouble of such manual operations, several automatic control devices have been proposed which act to automatically activate an electrically operated switch door or an electrically operated air purifier depending upon the degree of air pollution in the passenger compartment. For example, a Japanese Patent Early Publication No. 55-51615 discloses a control device which comprises gas sensors respectively provided outside and inside a passenger compartment and an electrically operated switch door for switching over from outside air induction to inside air induction in response to the degree of outside air pollution sensed by the outside gas sensor.
In Japanese Patent Publications Nos. 47-36974 and 47-36975, a control device is disclosed which comprises a gas sensor provided outside or inside a passenger compartment and means for switching over from outside air induction to inside air induction and vice versa in response to an output signal from the gas sensor. Furthermore, a Japanese Utility Model Early Publication No. 54-139442 discloses a control device for energizing an electrically operated air purifier of the recirculation type in response to activation of a cigarette lighter switch. In the above-mentioned control, either the air induction switch door or the air purifier, but not both, is independently operated under predetermined conditions. This means that when the switch door is in a position to allow the flow of recirculated inside air into the compartment due to pullution of the outside air, the polluted air in the compartment can not be purified. When the switch door is in a position to allow the induction of outside air, the air purifier is continuously operated over a long period of time.